The research to be supported by the funds requested is that undertaken by a cooperative group of pediatric oncologists who make up Children's Cancer Study Group A. The major objective of the group is to improve the treatment and survival of children with (1) acute leukemia and (2) solid tumors by means of protocol studies. (1) A protocol study for the treatment of acute lymphocytic leukemia is seeking to determine the best way to prevent CNS leukemia with the least toxicity. We need, also, to turn our attention to the problems created by marked immunosuppression from both radiotherapy and chemotherapy. Adding 2 more agents to the current treatment of acute granulocytic leukemia seems not to enhance response rate. New modes of therapy are being considered now. (2) Ongoing programs for the treatment of Wilms' Tumor rhabdomyosarcoma, neuroblastoma, and Ewing's Sarcoma are in progress. Programs need to be designed for osteogenic sarcoma and histiocytosis.